diff --git a/src/wifi/model/wifi-mode.cc b/src/wifi/model/wifi-mode.cc
index 65c56d08d..fa78548db 100644
--- a/src/wifi/model/wifi-mode.cc
+++ b/src/wifi/model/wifi-mode.cc
@@ -136,7 +136,7 @@ WifiMode::GetConstellationSize (void) const
   return item->GetConstellationSizeCallback ();
 }
 
-std::string
+const std::string&
 WifiMode::GetUniqueName (void) const
 {
   //needed for ostream printing of the invalid mode
diff --git a/src/wifi/model/wifi-mode.h b/src/wifi/model/wifi-mode.h
index 7b294650b..1860843d5 100644
--- a/src/wifi/model/wifi-mode.h
+++ b/src/wifi/model/wifi-mode.h
@@ -127,7 +127,7 @@ public:
    * \returns a human-readable representation of this WifiMode
    * instance.
    */
-  std::string GetUniqueName (void) const;
+  const std::string& GetUniqueName (void) const;
   /**
    * \returns true if this mode is a mandatory mode, false
    *          otherwise.
diff --git a/src/wifi/model/wifi-tx-vector.cc b/src/wifi/model/wifi-tx-vector.cc
index ab2df79c4..969f0b55e 100644
--- a/src/wifi/model/wifi-tx-vector.cc
+++ b/src/wifi/model/wifi-tx-vector.cc
@@ -337,7 +337,7 @@ WifiTxVector::IsValid (void) const
     {
       return false;
     }
-  std::string modeName = m_mode.GetUniqueName ();
+  const std::string& modeName = m_mode.GetUniqueName ();
   if (m_channelWidth == 20)
     {
       if (m_nss != 3 && m_nss != 6)